Support for additional Open API features (deferred)

[AlexanderAllen]

This issue is an epic. If I decide to ship anything mentioned here, I will cut such feature into it's own separate ticket.

The features listed here are supported by the Open API spec, but are currently not implemented, nor I necessarily deem them urgent for my personal use cases.

Therefore I'm capturing these features in this ticket for future reference.

• uniqueItems
• additionalProperties
• Required properties. Right now produced types are mostly nullable just to get the ball rolling. It would be nice to support required props across the board.
• Multiple variations of mixed type arrays, such as those containing both object literals mixed in with scalar types and references. This becomes rabbit-holey, but I am noting nonetheless that either more tests could be created, and/or more runtime assertions could be put in place to blunt the impact of any potentially silly recursions. Generated types are typically one-dimensional, with unions and intersections adding some depth, but PHPStan could offer limitless virtual type variations in arrays. Not sure Panettone would be the right place for interpreting mixed arrays into array shapes as again, that's a can of worms waiting to be opened.

Not supporting

• multilpleOf
• Multiple variations of min/max keywords
• Pattern

[AlexanderAllen]

Moving some inline comments from the test to here for future reference, and to clamp down on the test file size.

    // ADV_ALLOF_EDGECASE
    // TooManyRequests:
    // allOf:
    //   - $ref: '#/components/schemas/Error'
    //   - $ref: '#/components/schemas/Error'
    //   - type: object
    //     properties:
    //       spam_warning_urn:
    //         type: string
    //       some_other_ref:
    //         $ref: '#/components/schemas/Error'

    /**
     * Test for schema with a Type of "allOf".
     *
     * # This ...
     * TooManyRequests:
     *   allOf:
     *     - $ref: '#/components/schemas/Error'
     *     - type: object
     *       properties:
     *         spam_warning_urn:
     *           type: string
     *
     * # Should translate to this ...
     *   Class TooManyRequests
     *     public readonly ?Error $error = null
     *     public ?string $spam_warning_urn = null
     *
     * Notes:
     *   - cebe interprets the first $ref as an object, complete with inline properties ready for use
     *     when using `RESOLVE_MODE_ALL`. Adding these props straight away would result in inlined props
     *     and therefore duplicate props between types!
     *   - Both the first $ref Schema item and the second 'anonymous' Schema item have a cebe
     *     Schema type of `object`. Keep an eye on the conditions on the prop generator
     *     to prevent these getting mixed up.
     *
     * @TODO Test more complex edge cases w/ multiple and nested references. See ADV_ALLOF_EDGECASE above.
     *
     * @see https://swagger.io/docs/specification/data-models/oneof-anyof-allof-not/
     */